Monday, June 29, 2015

I'm going to kick off a series of posts that all feature fossils from the Kalkberg formation of New York with this specimen of Trematospira multistriata. It is a rounded, rectangular shaped shell with both valves showing some convexity. The shell is wider than long. Multiple thick costae decorate the surface of the shell and there is a wide sulcus that is best expressed on the pedicle valve. I base my ID on James Hall's "Paleontology of New York", Vol 3, Pt. 1, pg 209, & Pt 2, pl 28a, fig 5a-f

Brachial valve

Anterior

Pedicle valve

Posterior

Profile

The Kalkberg formation is lower Devonian in age (Lockhovian to Pragian stage). I collected this specimen from a roadcut near Shoharie, NY.

The only other Trematospira species I have posted about is Trematospira camara from the Silurian aged (Shienwoodian stage) Irondequoit limestone near Lockport, NY.

Saturday, June 27, 2015

On a collecting trip in May I found a specimen of the genus Phestia which I had read about but never found myself. Phestia is a very distinctive shell that looks like a giant comma. One end is rounded while the other sweeps away and narrows nearly to a point. Overall the shell has fine, yet distinct, concentric growth lines as the only decoration. According to Karl Wilson's book "Field Guide to the Devonian Fossil of New York", what I found is called Phestia brevirostra. It looks very similar to Nuculana rostellata (from the Arkona shale) and they could be synonyms or, at the least, close cousins.

I did a little more research into the naming of the species and it appears that Hall originally had a similar form listed as Leda rostellata in "Paleontology of New York", Vol 5, Pt. 1, pg 330, pl 47 and had a Leda brevirostris listed as well (pg 329, pl 47). The difference between the two was that L. rostellata has the elongated valves while L. brevirostris is shorter and less curved. I'm not sure at what point the genus was changed to Phestia as Leda is still valid. To add to the confusion, Conrad created the name Nuculana rostellata in 1841 ( T. A. Conrad. 1841. Fifth annual report on the paleontology of the state of New York. New York Geological Survey, Annual Report5:25-57) but I can't find a copy of that document which means I'm unable to compare the original descriptions or plates to Hall's from the Paleo. of NY.

To help try and clear up the issue, I posted this specimen and one from Arkona to a couple of Facebook groups. I was fortunate to have Gwen Daley respond in the group "The Devonian Period" and Dan O'Dea respond in the group "The Fossil Forum" both pointing me towards a paper called "Devonian Rocks and Lower and Middle Devonian Pelecypods of Guangxi, China and the Traverse Group of Michigan" and more specifically to Section G - "Systematic Paleontology of the Devonian Pelecypods of Guangxi and Michigan" by John Pojeta Jr., Zhang Renjie , and Yang Zuny. Within that section, on pages 64-65, is a discussion that essentially eliminates the use of Nuculana for Paleozoic pelecypods.

"For many years, Paleozoic opisthogyrate nuculaniform shells with fine external ornament were placed in the genus Nuculana (Link) (=Leda Schumacher)(pl. 3, fig. 10), which they closely resemble in shape (pl. 6; pI. 7, figs. 1-3, 12). McAlester (1962) suggested that the name Nuculana is inappropriate for Paleozoic species; in part, this was because Carboniferous species lack the pallial sinus of living forms. McAlester (1969b, p. N237, N239) limited the name Nuculana to Mesozoic and Cenozoic species and indicated that the name Phestia (Chernyshev) is appropriate for Devonian-Lower Triassic nuculanids that are not yoldiaform."

I've reproduced plate 6 from the paper which illustrates specimens of Phestia rostellata from the Hamilton group of both New York (fig 6-7) and Ontatio (fig 8-10).

In summary, I'm naming the fossil above, which I collected from the Windom shale member of the Moscow Formaiton (Devonian, Givetian stage) in Madison County, New York, and those specimens I've collected from the Arkona shale, and previously called Nuculana rostellata, what I feel is the proper name for both: Phestia rostellata (Conrad 1841) .

Thursday, June 25, 2015

The diversity of pelecypods that are found within the Devonian aged (Givetian stage) Moscow formation is pretty amazing. At a time when brachiopods were still somewhat dominant, pelecypods had become a strong part of the ecosystem in their own way. That is why I love it when I find another species that I've never seen before. Pholadella radiata is the muse of this post and is a nicely decorated shell that reminds me of the extant Arcidae family of shells. The specimens I found are all small, about an inch (2.5 cm) or so in length. It has a sweeping form on one side which contasts to the otherwise rectangular shape. Sharp radiating striae (lines on the surface of the shell that extend out from a common point) cross, generally, delicate concentric growth lines. It is this somewhat geometric decoration that makes it easy to ID in the field. I don't have any fully inflated specimens with both valves but you can see what they should look like in the pictures below.

This piece has numerous individuals all clustered together. It was part of a larger plate that broke apart as I was extracting it.

Here is a solo valve (the left valve I believe)

And a couple of right valves from different individuals.

All the pictured specimens come from the Deep Springs Rd. quarry near Earlville, NY which exposes the Windom shale member of the Moscow formation.

Tuesday, June 23, 2015

I'm not sure why but this trilobite makes me giggle a little bit when I hold it. Droptops megalomanicus is the largest trilobite species that I own and it is really cool to look at.This specimen comes from Jebel Mrakib near Alnif in the Tafilalet region of Morocco. The sheer size is rather amazing and reminds me of the Phacops rana trilobites that come from the Silica Shale. However the P. rana from the Silica Shale would get to be around 3-4" in length for a larger specimen while the one pictured below is 6-7" and they could get up to 8" in length.

I like how the trilobite "sits" on the rock. It is not perfectly prone, the pygidium and part of the thorax are slightly twisted and the whole body is slightly flexed. It lends more of an air of authenticity to me whereas something that is perfectly shaped and lain out looks more fake. Specimens of this species are commonly faked and I have seen plaster casts glued onto rock bases being sold as authentic.

Another special feature of this specimen is that the hypostome is preserved. You can see fine lines that are preserved on the hypostome and cephalon underside. These are called terrace ridges (because they sometimes look like contours on a topographical map) and are a good indicator that the specimen is authentic. Fakes do not preserve this level of detail.

Based on the paper by Bernd Kaufmann, "Facies,
stratigraphy and diagenesis of Middle Devonian reef-and mud-mounds in
the Mader (eastern Anti-Atlas, Morocco)." Acta Geologica Polonica 48 (1998): 43-106., Drotops megalomanicus is from the earliest part of the Givetian stage of the Devonian. He notes that D. megalomanicus is "abundant" within a layer below the Aferdou mud mound feature on Jebel Mrakib.

Sunday, June 21, 2015

Up today are a couple of Brachiopod specimens that I collected recently from the Mahantango formation in central Pennsylvania. The first specimen is a mold of a flat valve with many thin, narrow radial ribs covering the surface. To me this looks like a specimen of Protoleptostrophia perplana because it is similar to specimens I have from the Silica Shale, and the Windom Shale which are both contemporaneous with the Mahantango formation (Devonian, Givetian stage). This specimen came from the Frame Shale member and was found in Seven Stars, PA.

Closer views of the shell show features like possible epibionts that were attached to the exterior surface and variations in the growth of the ribs (due to life events that damaged or otherwise cased growth to change)

The second brachiopod came from the Montebello mbr. north of Harrisburg, PA. It is a rynchonellid that looks very similar to the genera Uncinulus. It is rouned in the cross section and (seemingly) narrows to a point at the posterior. The problem is that there is not enough detail preserved on the anterior for me to see what the margin looks like. If it is a strong "U" shape then I would go with Unicinulus. If the margin is not as strongly shaped then it could be a variety of Camarotoechia.

Friday, June 19, 2015

On a recent stop at one of my favorite Mahantango formation collecting spots, I came across this hash plate. It's presumably a record of a storm event which is why there is a diversity of fossil species and why they are jumbled together.

The stippled bar shape in this photo is likely a segment from the exoskeleton of the trilobite Dipleura. It is surrounded by impressions of a Spirifirid and some Chonetid brachiopods.

Here is the impression of a crinoid column segment. The five fold symmetry gives it away. I'm not sure what species it belonged to but it is nicely decorated. It appears that it was resting under a Chonetid type brachiopod shell but was exposed when I split the rock.

This is a fairly good impression of a Chonetid type brachiopod. By the size and shape I would lean towards Devonochoonetes coronatus but without the spines that line margin of the hinge line, I can't say for sure.

Lastly there is the impression of a pelecypod with some very fine, concentric growth lines. I would venture a guess that this is Nucula sp. similar to Nucula bellistriata like this one from the Panther Mountain formation of New York.

The Mahantango formation is Devonian in age (Givetian stage) and the portion I was collecting from is roughly equivalent to the Panther Mountain formation of New York. The exposure was a borrow pit near Seven Stars, PA in Juniata County.

Wednesday, June 17, 2015

One site that I like to collect at is most easily accessible in the spring since the undergrowth has not yet leafed out. It's an old quarry, which exposes the Montebello sandstone member of the Mahantango formation, that is many decades abandoned and yet one can still find some neat fossils there with a little searching. These three pelecypod shells came from one such collecting trip in April.

Cornellites flabella - Can easily be identified by the strong radial ribs and high angle of the body of the shell to the wing.

This appears to be a Pseudaviculopectin sp. pelecypod. the impression is somewhat faint and shallow but does resemble this specimen from the Windom Shale of New York.

Note the worm tube epibionts that are scattered on the surface of the shell.

Lastly is a shell impression that is more interesting for the epibiont that grew on it than the shell itself.

When you look close you can see some sort of rambling "trail" that maybe represents a coral like Aulopora or a bryozoan of some kind. There is not enough detail preserved for me to tell for sure.

All three specimens were collected from the Montebello Sandstone member of the Mahantango formation (Devonian, Givetian stage). It is roughly equivalent to the Panther Mountain formation of New York.

Monday, June 15, 2015

Since the fossils preserved in the Mahantango formation are often just molds or casts of the original shell, it can be difficult sometimes to try and ID what you have found. The specimen below is something I really have to think about. The shape tells me its a Strophomenid type brachiopod. The faint radial ribs are very fine and resemble a genera called Douvillina (like this one from the Centerfield mbr. of the Ludlowville formation in New York). I'm fairly confident that this fossil is a Douvillina sp. but the small "dents" that are in the center rear portion of the shell make we wonder if this is an internal cast of the pedicle valve. If this were the case then the "dents" would correspond to raised portions on the interior of the shell like the cardinal muscle attachment points.

A couple of closer views taken with different angles of light to highlight some of the features.

Note that you can see the impressions of the hinge teeth along the back edge of the cast.

This specimen was collected from the Montebello Sandstone member
of the Mahantango formation (Devonian, Givetian stage). It is roughly
equivalent to the Panther Mountain formation of New York.

Saturday, June 13, 2015

From the Ardennes region of Belgium comes this Ryocarhynchus tumidus brachiopod fossil. It was found in the Matagne Limestone (Fransian stage, Devonian) near the town of Robechies. The shell is round and wider than it is long. The brachial valve is very convex while the pedicle valve is slightly convex at the umbo and grades down to slightly concave in the sulcus. A single, gently dipping sulcus is present but is most pronounced at the anterior margin.

About Me

I'm a 40-something, life long student of Geology living in Philadelphia. My interests include Photography, Architecture and History among other things. When not cleaning my recent finds you'll find me in my backyard Hybridizing Daylilies or working in my garden. This Blog is an outlet for me to express my interest in fossils, catalog my collection and coalesce my thoughts and research into a useful medium.